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Clin Biomech (Bristol, Avon). 2017 Dec;50:130-138. doi: 10.1016/j.clinbiomech.2017.10.017. Epub 2017 Oct 19.

Biomechanics of anterior plating failure in treating distractive flexion injury in the caudal subaxial cervical spine.

Author information

1
Department of Spine Surgery, Institute of Surgery Research, Daping Hospital, Third Military Medical University, Chongqing, China.
2
Chongqing Key Laboratory of Vehicle Crash/Bio-Impact and Traffic Safety, Department 4, Institute of Surgery Research, Daping Hospital, Third Military Medical University, Chongqing, China.
3
Shandong Weigao Orthopedic Device Company LIMITED, No 26 Xiangjiang Road, Tourist Resorts, Weihai City, Shandong Province, China.
4
Department of Spine Surgery, Institute of Surgery Research, Daping Hospital, Third Military Medical University, Chongqing, China; Department of Orthopaedic Surgery, Chongqing Emergency Medical Center, The Fourth People's Hospital of Chongqing, Chongqing, China.
5
Department of Orthopaedic surgery, Kunming General Hospital, Yunnan, China.
6
Institute of Digital Medicine, Third Military Medical University, Chongqing, China.
7
Department of Mechanical Engineering, Embry-Riddle Aeronautical University, Daytona Beach, FL, USA.
8
Department of Spine Surgery, Institute of Surgery Research, Daping Hospital, Third Military Medical University, Chongqing, China. Electronic address: zhaojianhua1964@163.com.
9
Department of Spine Surgery, Institute of Surgery Research, Daping Hospital, Third Military Medical University, Chongqing, China. Electronic address: Liupengd@163.com.

Abstract

BACKGROUND:

Operative level is a potential biomechanical risk factor for construct failure during anterior fixation for distractive flexion injury. No biomechanical study of this concept has been reported, although it is important in clinical management.

METHODS:

To explore the mechanism of this concept, a previously validated three-dimensional C2-T1 finite element model was modified to simulate surgical procedure via the anterior approach for treating single-level distractive flexion injury, from C2-C3 to C7-T1. Four loading conditions were used including no-compression, follower load, axial load, and combined load. Construct stability at the operative level was assessed.

FINDINGS:

Under these loading conditions with the head's weight simulated, segmental stability decreases when the operative level shifts cephalocaudally, especially at C6-C7 and C7-T1, the stress of screw-bone interface increases cephalocaudally, and in the same operative level, the caudal screws always carries more load than the cephalad ones. All these predicted results are consistent with failure patterns observed in clinical reports. In the contrast, under other loading conditions without the weight of head, no obvious segmental divergence was predicted.

INTERPRETATION:

This study supports that the biomechanical mechanism of this phenomenon includes eccentric load from head weight during sagittal movements and difference of moment arms. Our study suggests that anterior fixation is not recommended for treating distractive flexion injury at the caudal segments of the subaxial cervical spine, especially at C6-C7 and C7-T1, because of the intrinsic instability in these segments. Combined posterior rigid fixation with anterior fixation should be considered for these segments.

KEYWORDS:

Anterior plate; Biomechanics; Cervical spine trauma; Finite element analysis

[Indexed for MEDLINE]

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